1. Field of the Invention
The present invention relates to an automatic transmission locking mechanism for an automatic transmission for a vehicle and more particularly to an automatic transmission locking mechanism for an automatic transmission of a reduced axial dimention for a vehicle.
2. Description of the Prior Art
In most front-engine front-drive automobiles (designated as "FF automobiles" hereinafter), the engine is mounted transversely. Accordingly, the axial dimension of an automatic transmission for an FF automobile is required to be reduced, particularly when the engine is mounted transversely.
Most conventional automatic transmission locking mechanisms interlocked with a manual shift lever employ the following constitution. That is, a lever is joined integrally to a manual shaft which is turned through the manual operation of a manual shift lever, the rear end of a cam rod provided intermediately with a cam is linked to the lever and the free end of a pole with a detent is pushed up and thereby the pawl is turned about the axis of turning thereof when the cam is caused to run on a slope formed in a bracket supporting the front portion of the cam rod extending forward from the cam, whereby the detent engages with a parking gear fixed to the output shaft of the transmission to lock the output shaft. A spring mechanism in included the automatic transmission locking mechanism to retain the pawl with the detent at the released position while the vehicle is running so that the detent will not be brought into contact with the parking gear while the vehicle is running.
When such an automatic transmission locking mechanism is applied to an automatic transmission for an FF automobile in which the manual shaft and the shaft provided with the parking gear are disposed remotely from each other and in distantly stepped planes, the distance between the center of turning and the cam engaging surface of the pawl with the detent is increased due to the distant relative disposition between those shafts and hence an increased relative slip in a direction perpendicular to the direction of advancement of the cam between the cam and the cam engaging surface occurs when the pawl with the detent is turned and thereby the movement of the cam is impeded and the wear of the cam is accelerated. Furthermore, such a constitution inevitably requires an elongate pawl with a detent, therefore, the weight of the pawl is increased and the pole is inclined, so that the movement of the cam is further impeded and the wear of the cam is further accelerated.